Rolling ball tachometer



y 1951 c. H. ANDERSON, JR 2,551,717

ROLLING BALL TACHOMETER Filed July 3, 1947 2 Sheets-Sheet 1 3 rw ma/bo a UM r/es [ff/Mama, c/Z,

Patented May 8, 1951 ROLLING BALL TACHOMETER Charles H. Anderson, J12, Peters Township, Washington County, Pa.

Application July 3, 1947, Serial No. 758,801

9 Claims.

This invention relates to tachometers, and more particularly to tachometers of the centrifugally actuated type.

A main object of the invention is to provide a novel and improved tachometer which is very simple in construction, easy to read and not subject to being thrown out of calibration.

A further object of the invention is to provide an improved tachometer which is inexpensive to manufacture, sensitive in operation and reliable in performance, the operation of the tachometer being based on well known physical laws and the device being free of any errors due to changes in calibration, since its calibration is constant.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure l is an elevational View of a tachometer constructed in accordance with the present invention.

Figure 2 is an enlarged cross-sectional view taken on line 2--2 of Figure 1.

Figure 3 is a cross-sectional view taken on line 3-3 of Figure 2.

Referring to the drawings, ll designates a bottom housing member having removably secured thereto a bottom cover plate l2. Threaded into the top wall of housing member II is the neck portion I3 of a bowl member l4 formed of transparent plastic material whose outer surface is smoothly polished and whose inner surface is roughened or etched to form a light diffusing surface. Neck portion [3 has secured thereto a stationary vertical bearing sleeve and journalled in bearing sleeve [5 is an inner sleeve I6 having a flange ll rotatively bearing on the top of bearing sleeve 15. Secured to the top of inner sleeve 16 is a transparent or translucent cup member 18 whose peripheral surface is closely adjacent to but not in contact with the inner surface of bowl member [4. Secured to the lower end of inner sleeve I6 is a spiraltoothed worm gear l9. Worm gear I!) is in mesh with a spiral-toothed worm gear 20 carried on a horizontal shaft 2| journalled in a side wall of bottom housing member ll. Shaft 2| is adapted to be connected by any suitable means, as by a conventional flexible shaft, to the shaft or spindle whose speed is to be measured.

The peripheral surface of cup member I8 is formed with a plurality of vertically extending equally spaced grooves 22 and in each of said grooves is positioned a spherical steel ball 23 adapted to roll up the inner curved surface of bowl member [4 under the effects of centrifugal force developed responsive to the rotation of said bowl member.

The bottom surface of cover plate I2 is formed with a central recess 24 and secured in said recess is an annular member 25 carrying a vertical sleeve 26 which projects upwardly through sleeve I6 into cup member l8. Secured to the top end of sleeve 26 is an electric socket 21 in which is mounted a lamp bulb 28. A suitable electric cord is connected to socket 21 and passes downwardly through sleeve 26 to a source of current.

The bottom housing II is provided with base lugs 29, 29 for securing the housing to a suitable stationary horizontal support.

The outer surface of bowl member M is marked with a series of calibration rings 36 numbered to indicate various shaft speeds. When shaft 2| is coupled to a shaft whose speed is to be measured, the rotation of said shaft 2| is transmitted to cup member l8 by spiral worm gears 2E3 and I9 which drive the rotary sleeve l5 carrying said cup member. The steel balls 23 are whirled around the curved inner peripheral surface of bowl member I4 by the grooves 22 and under the efiects of centrifugal force climb to a position of equilibrium on the curved inner peripheral surface of the bowl member determined by the angular rotational velocity of the cup member. The rotating balls 23 intercept light from the lamp 28 and produce a dark band on the illuminated surface of the bowl member l4. By observing the position of said band with respect to the calibration rings 39 the rotational velocity of shaft 2| may be readily determined.

Since the equilibrium position of the balls 23 is a function only of the speed of rotation of said balls and is independent of their weight, wear of the balls will not change the calibration of the instrument. The rolling action of the balls reduces friction to a minimum, which gives the instrument great sensitivity. The balls rotate, at a substantial speed, so that they have considerable inertia. This makes the instrument very stable and minimizes hunting. Due to the reduction of friction, wear is negligible and only a very light load is imposed on the driving components of the instrument. This insures long life and reliable performance thereof.

To protect the interior of the bowl member l4 against the entry of dirt or dust, a top cover 3| is secured thereto, said cover being removable face should be accurately a surface of revolution.

The range of the instrument may be changed by suitably varying the steepness of the inner flaring contour of the bowl member.

While a specific embodiment-of a tachometer device has been disclosed in the foregoing description, it will be understood thatvarious modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention other than as defined by the scope-of the appended claims.

What is claimed is:

1. A tachometer, comprising a stationary bowl member of light-transmitting material-,said bowl member having an inner surface formed w upwardly-flaring internal contour, a free 1 member in said bowl member, a rotary coaxially mounted in said bowl mein rotary member engaging said free rolling member and rollably holding the same against said inner surface of said bowl member, and means for connecting said rotary member to a shaft whose speed is to be measured whereby to rotate rotary member.

2. A tachometer, comprising a stationary bowl member of light-transmitting material, said bowl member having an inner surface formed with an upwardly-flaring internal contour, an opaque free rolling member in said bowl member, a cupshaped rotary member of translucent material coaxially mounted in said bowl member, said rotary member engaging said free rolling member and rollably holding the same against said inner surface of said bowl member, means for connecting said rotary member to a shaft whose speed is to be measured whereby to rotate said rotary member, and a stationary light source supported ber and disposed in slightly inwardly-spaced eon-v centric relation thereto, said periphery of said rotary member being formed with an upwardlyextending groove, said free rolling member being freely rollably seated in said groove and on said inner surface of said bowl member, and means for connecting said rotary member to a shaft whose speed is to be measured whereby to rotate said rotary member.

4. A tachometer, comprising a stationary bowl member of light-transmitting material having an inner surface formed with an upwardly-flaring internal contour, a cup-shaped rotary member of translucent material coaxially mounted in said bowl member, said rotary member having an outer periphery complementary to said inner sur-r' 4 face of said bowl member and disposed in slightly inwardly-spaced concentric relation thereto, said periphery of said rotary member being formed with an upwardly-extending groove, an opaque ball freely rollably mounted in said groove and on said inner surface of said bowl member, means for connecting said rotary member to a shaft whose speed is to be measured whereby to rotate said rotary member.

5. A tachometer, comprising a stationary bowl member of light-transmitting material havin an inner surface formed with an upwardly-flaring internal contour, a cup-shaped rotary member of translucent material coaxially mounted in said bowl member, said rotary member having an outer periphery complementary to said inner surface of said bowlmember and disposed in slightly inwardly-spaced concentric relation thereto, said periphery of said rotary member being formed with an upwardly extending groove, an opaque ball freely rollably mounted in said groove and on said inner surface of said bowl member, means for connecting said rotary member to a shaft whose speed is to be measured whereby to rotate said rotary member, light, and said bowl member including an outer surface formed and inscribed with a vertical scale adapted to cooperate with said ball to designate shaft speeds.

6. A tachometer, comprising a bowl member of light-transmitting material having an upwardly-flaring internal contour providing a surface of revolution about a vertical axis, a hollow upwardly-directed cup-shaped rotor of translucent material, said rotor being coaxially journaled in said bowl member, said rotor havin an outer periphery complementary to said surface of said bowl member and which is disposed in inwardly-spaced concentric relation thereto, said periphery being formed with a plurality of equally-spaced vertically-extending grooves, an opaque ball bearing freely roliable in each groove and adapted to roll on said internal surface of said bowl member, means for connecting said rotor to a shaft whose speed is to be measured, and said bowl member having an outer surface calibrated with a series of vertically-spaced horizontal ring markings representing different shaft speeds.

7. A tachometer comprising a base, an outer stationary translucent conical cup mounted vertically upon said base, an axial tubular bearing in the lower end of said cup, an inner rotary translucent conical cup concentrically spaced from and positioned within said stationary cup, an axial shaft on the lower end of said inner cup supportably journalled in said tubular bearing, the external surface of said inner cup being formed with a vertical groove extending from the lower part to the upper part thereof, a free ball confined in said groove and rolling on the inner surface of said outer cup, and means on said base for connecting to said shaft another shaft to be speed tested.

8. A tachometer comprising a base, an outer stationary translucent conical cup mounted vertically upon said base, an axial tubular bear- 111g in the lower end of said cup, an inner rotary translucent conical cup concentrically spaced from and positioned within said stationary cup,

an axial shaft on the lower end of said inner cup supportably journalled in said tubular bearing, the external surface of said inner cup being formed with a vertical groove extending from the lower part to the upper part thereof, a free ball confined in said groove and rolling on the inner surface of said outer cup, and means on said base for connecting to said shaft another shaft to be speed tested, said groove opening through the upper end of said inner cup, and a cover closing the upper end of said outer cup having a portion closing the upper end of said groove and acting as a stop for said free ball.

9. A tachometer comprising a base, an outer stationary translucent conical cup mounted vertically upon said base, an axial tubular bearing in the lower end of said cup, an inner rotary translucent conical cup concentrically spaced from and positioned within said stationary cup, an axial shaft on the lower end of said inner cup supportably journalled in said tubular bearing, the external surface of said inner cup being formed with a vertical groove extending from the lower part to the upper part thereof, a free ball confined in said groove and rolling on the inner surface of said outer cup, and means on said base for connecting to said shaft another shaft to be speed tested, said shaft being tubular, a standard stationarily mounted on said base and passing freely upwardly through said tubular shaft into the interior of said inner cup, and a lamp mounted on said standard within said inner cup for silhouetting said ball.

CHARLES H. ANDERSON, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

